A member of the Bureau of Land Management Silver State Hotshot crew from Elko, Nev., walks through a burn operation on the southern flank of the Rim Fire. / Mike McMkillan, U.S. Forest Service, via AP

by John Bacon, USA TODAY

by John Bacon, USA TODAY

YOSEMITE NATIONAL PARK, Calif. - Firefighters gained ground Monday on a massive wildfire on the edge of California's Yosemite National Park, but the fire grew to 357 square miles and complete containment remained almost three weeks away, authorities said.

The California Department of Forestry and Fire Protection reported that the Rim Fire was 60% contained Monday, up from 45% containment Sunday night. The agency said 4,500 homes remained threatened by the blaze, but few mandatory evacuations remained in place.

More than 4,600 personnel were battling the blaze, aided by more than 300 fire engines and 14 helicopters. Full containment was not expected until Sept. 20, the agency said.

The blaze started Aug. 17 in the Stanislaus National Forest and two-thirds of the land burned since then is located there. The cause remained under investigation.

Clouds and higher humidity had slowed flames from advancing through brush and trees on Sunday, giving firefighters room to set backfires, dig containment lines and to strengthen lines around threatened communities, fire spokesman Trevor Augustino said.

The Rim Fire is the state's fourth largest dating back to 1932. It's burning an area larger than the cities of San Francisco, Oakland and San Jose combined, agency spokesman Daniel Berlant said.

A 427-square-mile fire in San Diego County that killed 14 people and destroyed more than 2,800 structures a decade ago tops the list of California's largest wildfires.

The Rim Fire has resulted in five injuries and no deaths. Eleven homes have burned, but the dense smoke that obscured Yosemite's majestic views for the first time on Saturday and prompted air quality warnings was starting to ease, park spokeswoman Kari Cobb said.

Although park officials advised visitors to avoid heavy exertion, Cobb said she has seen people outside running "and enjoying Yosemite, despite the smoke."